The objective of this proposal is to continue our work in the characterization in man of some of the substrate and hormonal factors which regulate the metabolism of plasma branched chain amino acids (BCAA) and their role as nitrogen sources for alanine, a major precursor for glucose production by the liver. Since it is well established that glucose production from alanine is increased in diabetes and since this is associated with increased blood levels of BCAA, conceivably BCAA (by serving as a nitrogen source for alanine) may be involved in sustaining abnormal glucose production in diabetes mellitus. The BCAA, leucine, isoleucine and valine, are essential amino acids since they cannot be synthesized de novo in man. In vivo studies by ourselves suggest that as much as 50-70 percent of alanine nitrogen might be derived from the catabolism of BCAA. Little is known of the metabolic and hormonal factors which regulate the production and utilization of the BCAA and their interrelationship with alanine production in normal and diabetic man. This proposal will utilize recently developed stable isotopic techniques and classical tritiatedglucose and 14C alanine isotope dilution methodology to investigate the effects of insulin, cortisol, epinephrine, and growth hormone, as well as alterations in plasma glucose, free fatty acids and ketone bodies on the rates of appearance and disappearance of plasma leucine, glucose and alanine; the incorporation of leucine nitrogen into alanine; and gluconeogenesis from alanine in normal and diabetic man. Deuterium labeled leucine and U-14C alanine will be utilized to determine the flux of these two amino acids, 15N leucine will be used to assess the rate of transfer of leucine nitrogen into the circulating alanine pool and 14C-incorporation into glucose from alanine will determine the relative contribution of alanine for gluconeogenesis. These studies will permit us to gain a better understanding of the diverse actions of insulin, cortisol, epinephrine, growth hormone, and other metabolic intermediates on carbohydrate, protein and fat metabolism. Only through a more thorough understanding of the biochemical events in the regulation of fuel metabolism in normal and diabetic man can we evaluate the consequences of and modify our current approach to therapy.